Exhaust manifold device

ABSTRACT

An exhaust manifold device is provided to allow air to enter an exhaust manifold during normal operation of an engine to prevent exhaust gases being sucked into the cylinders via exhaust valves. Air can be supplied via valves (18 and 21) to the exhaust manifold as required and is supplied to the valve (21) at pressures, above atmospheric pressure, that increase with engine speed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to exhaust manifold devices.

2. Description of the Related Art

The invention relates more particular to devices that are arranged toautomatically allow air to enter the exhaust manifold to prevent interalia exhaust gases being sucked into engine cylinders during the normaloperation of the engine. Such devices or aspirators have been disclosedalready in, for example, U.S. Pat. No. 3,455,106 and European Patent0041831. Devices so far proposed comprise relatively complicatedmechanical arrangements and do not operate efficiency at higher enginespeeds or at a variety of engine speeds.

It is an object of the invention to overcome or at least reduce theseproblems,

According to the invention there is provided an aspirator for allowingair automatically to selectively enter an engine exhaust manifold duringoperation of an internal combustion engine to inhibit exhaust gasesbeing drawn back into the cylinders via exhaust valves, the aspiratorcomprising an adapter that fits to the manifold having a port incommunication with the manifold, a first one way valve fitted to theadapter that prevents gases leaving the manifold through the port whenthe pressure inside the manifold is greater than the pressure at thefirst valve, and a second one way valve connected by a passageway to thefirst valve, the second one way valve being arranged to allow air toenter the passageway whenever the pressure inside the passageway is lessthan the pressure at the second valve; and means for supplying air tothe second valve at different pressures, above atmospheric pressure,that increase with increases of speed of the engine.

The aspirator may comprise a hollow body that extends to the port fittedto the manifold and the port be formed in a tube that extends somewhatin to the manifold beyond its inner surface.

The hollow body may be formed with an intermediate expansion chamber.

The one way valves may each comprise a needle valve.

The passageway is preferably formed with an intermediate expansionchamber.

The position of the second one way valve may be manually adjustable tovary the differential pressure at which the second valve opens andcloses.

The air may be supplied to the second one way valve by an air ram havingan inlet exposed forwardly in a vehicle in which the engine is mountedso as to provide air at a pressure corresponding to the forward speed ofthe vehicle.

The air may also or alternatively be supplied by an air pump, and theair pump may form part of a turbo charger for the engine.

An exhaust manifold device or aspirator according to the invention willnow be described by way of example with reference to the accompanyingschematic drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view of an adapter of the device;

FIG. 2 in a sectional side view of the device which fits above theadapter in use;

FIG. 3 is a top plan view of an exhaust manifold; and

FIG. 4 is a top plan view of the device in a turbo charger applicationof the device.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings, in FIG. 1 the adapter comprises a lower part10 including a port 11 that screw fits to an engine manifold 12. Thelower part incorporates an expansion chamber 13 that is closed off byhollow cap 14 extending up to a gland fitting 15 which seals andconnects the cap 14 to a cylindrical tube 16.

It will be noted that the bottom edge of the port 11 extends somewhatinto the manifold 12 and beyond its inner surface. This makes the portmore sensitive to the flow of gases and pressure in the manifold. Also,hot exhaust gases are less inclined to be swept into the port 11 andcorrode valve seatings in the device. The provision of the expansionchamber 13 ensures that any flow of air towards the manifold isaccelerated and so "rammed" through the port 11, when required, into themanifold.

In FIG. 2, the tube 16 is attached to a lower housing 17 incorporating afirst one way needle valve 18 by a gland coupling 19. An upper housing20 is slidably or otherwise adjustably attached to the lower housing 17so that the housings together form an expansion chamber 20'. Theeffective size or capacity of the chamber 20' can be varied as and whenrequired but serves as a pressure damper between the first valve 18 anda second one way needle valve 21. The valve 21 is biassed by a spring 22and fitted to an upper end of the housing 20 by a screw thread so thatmanually adjustment can be made to increase or decrease the effectivespring bias. This adjustment enables the differential pressure at whichthe valve 21 opens and closes to be varied. The device includes two highpressure bi-pass and relief ports 22' and 23.

In general, the device is provided to allow air to enter the exhaustmanifold from atmosphere via the valves 18 and 21 as and when required,and as already known in principle in the prior art. In devices of thepresent invention air is supplied to the valve 21 under pressure whenthe engine speeds up so that a supply of pressurised air is providedthrough the port 11 to ensure efficient operation at all times. Thepressurised air is preferably supplied for the exhaust of a movingvehicle by feeding air from a forward facing inlet. Thus, as vehiclespeeds up the pressure of the air supplied to the valve 21 automaticallyincreases to correspond to the engine speed and provide a supply ofincreased pressurised air to the port 11 as desired. The pressurised aircan also be supplied from an electric fan, say, or a turbo charger fan,as shown in FIG. 4.

FIG. 3 shows at 30, a central preferable location for fitting the deviceto a manifold of a four cylinder engine. The location is chosen tocoincide with a region where the flow of exhaust gases is mixedgenerally evenly from all four cylinders. It is of course possible touse other locations or provide more than one device in which case thechoice of location will depend on which and an how many cylinders areserved by each device.

In FIG. 4, the device of the invention is provided with air at elevatedpressure as required from a bleed-valve 31 connected to an outlet of aturbo charger fan 32. The outlet air is normally fed to force fuel-airmixture into the engine cylinders but a sufficient amount is used, thatis diverted or bled, to create a supply and elevated pressure of air atthe inlet to the needle valve is of the device.

What is claimed:
 1. An aspirator for allowing air automatically toselectively enter an engine exhaust manifold during operation of aninternal combustion engine to inhibit exhaust gases being drawn backinto the cylinders via exhaust valves, the aspirator comprising anadapter formed by a hollow body that extends to a port fitted incommunication with the manifold, a first one way valve fitted to theadapter that prevents gases leaving the manifold through the port whenthe pressure inside the manifold is greater than the pressure at thefirst valve, and means for supplying air to a second one way valve atdifferent pressures, above atmospheric pressure, that increase withincreases of speed of the engine, in which the second one way valve isconnected by a passageway to the first valve forming an intermediateexpansion chamber having a relief port to atmosphere, the second one wayvalve being arranged to allow air to enter the passageway whenever thepressure inside the passageway is less than the pressure at the secondvalve.
 2. The aspirator of claim 1, wherein the port is formed in a tubethat extends into the manifold beyond its inner surface.
 3. Theaspirator of claim 1, wherein the one way valves each comprises a needlevalve.
 4. The aspirator of claim 1, wherein the position of the secondone way valve is manually adjustable to vary the differential pressureat which the second valve opens and closes.
 5. The aspirator of claim 1,wherein the air is supplied to the second one way valve by an air ramhaving an inlet exposed forwardly in a vehicle in which the engine ismounted so as to provide air at a pressure corresponding to the forwardspeed of the vehicle.
 6. The aspirator of claim 1, wherein the air issupplied by an air pump.
 7. The aspirator of claim 6, wherein the airpump forms part of a turbo charger for the engine.
 8. The aspirator ofclaim 1, in which air is supplied to the second valve corresponding toall speeds of the engine.